The present invention relates to a developing apparatus to be used in electrophotographic printers, copying machines, facsimile machines and the like, and a method of manufacturing the same
In a conventional developing apparatus, toner serving as developer is supplied to a development roller which is rotating, and is then conveyed to a position where it is pressed by a developer regulating member. The toner conveyed to the developer regulating member while being held on the outer surface of the development roller is pressed by the developer regulating member into a thin layer of a predetermined thickness. At this time, the toner is charged, so that a charged toner layer is formed on the outer surface of the development roller. The toner of the charged toner layer is directly supplied to a photoconductor opposed to the development roller. The Japanese Published Unexamined Patent Application, Publication No. Hei 3-48876, discloses an example of the developing apparatus thus structured.
FIG. 20 is a cross-sectional view showing the structure of a relevant part of the developing apparatus disclosed in the Japanese Published Unexamined Patent Application, Publication No. Hei 3-48876. In the conventional developing apparatus shown in FIG. 20, in a toner space 105 containing toner serving as developer, toner is supplied to the outer surface of a development roller 107 by the rotation of a fan 106 in the direction of the arrow b, and is held thereon. The toner held on the development roller 107 is conveyed in the direction of the arrow a as the development roller 107 rotates. As shown in FIG. 20, a bent portion 108a in the vicinity of an end of a blade 108 serving as the developer regulating member is pressed against a pressed portion 109 of the development roller 107. The bent portion 108a is bent outwardly with respect to the development roller 107 so as to form an arc.
Consequently, the thickness of the layer of the toner held on the development roller 107 is regulated by the blade 108 at the pressed portion 109, and unnecessary toner is swept off. The toner regulated at the pressed portion 109 is charged by being in contact with the blade 108, so that a thin layer of the charged toner is formed on the outer surface of the development roller 107 having passed the pressed portion 109.
The toner thin layer thus formed on the development roller 107 is conveyed to a development area 111 opposed to a photoconductor 110, and a toner image is formed on an electrostatic latent image formed on the outer surface of the photoconductor 110.
In the conventional developing apparatus thus structured, the bent portion 108a formed in the vicinity of the end of the blade 108 serving as the developer regulating member is bent so as to form an arc. Since toner is held in a wedge-shaped space in the upstream side of the bent portion 108a, toner does not heap uniformly. Consequently, the blade 108 of the conventional developing apparatus is low in the capability of accurately forming the toner thin layer so as to have a predetermined thickness, and is low in the capability of sufficiently charging the toner of the thin layer. Moreover, in the conventional developing apparatus, since the toner on the outer surface of the development roller 107 is pressed by the arcing bent portion 108a of the blade 108, it is necessary that the pressure applied from the blade 108 to the development roller 107 be high, so that the development roller 107 requires a large driving force. Moreover, it is difficult to form a uniform layer since streaks are generated on the toner layer on the development roller 107 or some of the toner is scraped off from the toner layer